1. Mini-Pascal Compiling Mini-Pascal (MPC) language
Subset of the Pascal programming language
Somewhat similar to the Java and “C” programming languages
There are many differences, however
Differences make it much easier to compile ☺
We will discuss details of the actual language when it becomes important

2. Scanning 1st stage of compiling a program
Code written in a programming language
High-level languages are supposed to resemble English…
…but they don’t.
Contain many features specifically designed for the computer
How often do you use a semi-colon?

3. Scanning Raw text is hard for computer to understand
Much easier for it to work with objects
Scanning converts text into tokens
Object encoding a single text idea
This is a very common problem, not just in compilers

4. Scanning Only consider token being processed
This stage of compilation only generates tokens
Looks for obvious lexical errors --- text that cannot be legal
Does not track past tokens
Does not worry if text has any real meaning
Understanding meaning occurs later in the process

5. Lexical analysis for tokens in English
Legal: ? “”, Snap p. 35 crackle < pop ppo quack!
Illegal: ¡ I am excited !
Illegal: gemütlichkeit façade

6. Lexical analysis for tokens in English
Legal: ? “”, Snap p. 35 crackle < pop ppo quack!
Illegal: ¡ I am excited !
Illegal: gemütlichkeit façade

7. Types of Tokens in Mini-Pascal
Operator
All the meaningful symbols in Mini-Pascal:
Numerical: + - * ^
Comparative: < > <= >= <> ==
Separator: ( ) [ ] . ; ,
Assignment: :=
Spaces are meaningful
“:=” is one token
“: =” is two tokens

8. Types of Tokens in Mini-Pascal
Int
Includes all numbers defined by Mini-Pascal
Mini-Pascal does not include real numbers
Int token includes an uninterrupted series of integers
“ ” is one token
“13 45” is two tokens – for “13” and “45”
“13.65” is three tokens – for “13”, “.”, and “65”
“2,585” is three tokens – for “2”, “,”, and “585”

9. Types of Tokens in Mini-Pascal
String
The literal strings in Mini-Pascal
Java strings begin and end with double quote (“”)
Pascal strings begin and end with single quote (‘’)
Can include any set of characters, letters, and numbers, but cannot go across multiple lines
‘Hi Mom. #1’ is one token -- “Hi Mom. #1”
Note: The quotes are not included in the token

10. Types of Tokens in Mini-Pascal
Identifier/Id
Includes keywords (reserved) in Mini-Pascal: and array begin case const div do downto else end for function if mod nil not of or procedure program record repeat then to type until var while
Also potential variable and method names
Begin with letter and then any combination of letters and numbers
DO NOT worry (yet) if it is an actual name

11. Other Work While Scanning
Comments
Pascal also includes comments
Begins with either a “{“ or “(*”
Then include any legal characters including letters, numbers, spaces, newlines
End with either “}” or “*)”
{ This is a legal comment *) (* and so is this }
There is no comment token --- it is not used in compilation